Initial conditions for Starobinsky inflation in general quadratic gravity

TL;DR

This paper investigates initial conditions for Starobinsky inflation within a generalized quadratic gravity framework, demonstrating that inflation can occur without fine-tuning despite additional curvature terms.

Contribution

It extends the analysis of initial conditions for Starobinsky inflation to a more general quadratic gravity model with an extra curvature squared term, maintaining stability.

Findings

Inflation can be achieved without fine-tuning initial conditions.

The presence of an additional curvature squared term alters the initial condition landscape.

Stable inflationary solutions are possible in the generalized quadratic gravity model.

Abstract

We consider initial conditions leading to Starobinsky inflation in the general quadratic gravity, where the action of the theory contains one more curvature square invariant in addition to $R^2$. We have chosen corresponding coefficients in a way so that the inflationary solution keeps to be stable. Our numerical results show that despite the configuration of initial conditions in the $(H,R)$ plane, leading to Starobinsky inflation can change considerably from the $R^2$ theory, realization of inflation does not need a fine-tuning of the initial conditions.